Disc replacement device and method of use

ABSTRACT

A disc replacement device including a first body member with a convex articulation surface and a second body member with a concave articulation surface is disclosed. When operably positioned, the convex articulation surface engages the concave articulation surface to provide for movement therebetween. The disc replacement device also includes a first opening in the first body member and a second opening in the second body member, wherein the openings are angled and extends from the front aspects of the body members through the external surfaces. The disc replacement device further includes at least two bone fasteners for insertion into the first and second openings to secure the disc replacement device to a first and second vertebra. An interbody motion device and fusion implant, as well as a surgical method for implantation are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/342,226 filed on May 20, 2014 (U.S. Pat. No.9,820,864) which application was a 371 Application of PCT ApplicationNo. PCT/US2012/053423 filed on Aug. 31, 2012, which claims the prioritybenefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent ApplicationNo. 61/530,237 filed Sep. 1, 2011, each of which is incorporated hereinby reference in their entireties.

TECHNICAL FIELD

The present invention relates generally to general surgery, orthopaedicand neurosurgical implants used for insertion within a space betweenhard tissue structures, and more specifically, but not exclusively,concerns devices implanted between vertebral bodies to replace aresected or diseased intravertebral disc to maintain or reestablishproper spacing between two vertebral bodies.

BACKGROUND OF THE INVENTION

Damage or disease that affects the integral structure of the spine, maylead to neurologic impairment or loss of structural support integritywith possible permanent damage to the surrounding soft tissue andadjacent neurologic, vascular and systemic structures. Maintaining orreestablishing anatomic spacing within the spinal column is critical toensuring continued functionality and mobility of the patient andavoidance of long-term serious neurological, vascular or other systemicimpairments.

SUMMARY OF THE INVENTION

Advancement of the state of interbody devices and implants and thesurgical management relating to the clinical presentation of damagedtissue structures between two vertebral bodies is believed desirable.Two examples of embodiments of the invention that satisfies the need forimprovements to an interbody disc device used to treat patientssuffering from either a diseased or damaged disc includes at least onemoveable top member and a stationary bottom member that is slidinglycoupled to the moveable top member.

The present invention provides in one aspect, a disc replacement devicethat has a first body member that includes a convex articulation surfaceand a second body member including a concave articulation surface. Whenoperably positioned, the convex articulation surface of the first bodymember engages the concave articulation surface of the second body.

In another aspect of the present invention, the disc replacement devicehas a generally cylindrical geometry. The first body member alsoincludes an external inferior surface and a top internal surface and thesecond body member includes an external superior surface and a bottominternal surface. The external superior surface and external inferiorsurface are arcuate. The top internal surface of the first body membermay include a flat portion with a convex portion in a generally centralposition on the flat portion and extending away from the flat portion tocreate the convex articulating surface. The bottom internal surface ofthe second body member including a flat portion with a concave portionin a generally central position on the flat portion and extending intothe second body member from the flat portion to create the concavearticulating surface.

In a further aspect of the present invention, the disc replacementdevice may include first and second openings in the first and secondbody members where the first and second openings are angled and extendfrom a front aspect of the first and second body members through theexternal surfaces. The angled openings include an angle ranging fromabout 10° to about 45°. The disc replacement device may further includeat least two bone fasteners for insertion into the first and secondopenings to secure the device to a first and second vertebra.

The present invention provides in another aspect an interbody motiondevice that includes a bottom body member having a convex surface, a topbody member having a channel, and a bearing member having a concavesurface. The bearing member is connected to the channel with the concavesurface of the bearing member engaging the convex surface of the bottombody member when the device is in use. The interbody motion devicewherein the concave surface of the bearing member is configured topermit at least one of translation and rotation of the convex surface ofthe bottom member. The interbody motion device may also include anoutside surface that is generally arcuate. The interbody motion devicefurther comprising first and second openings extending from the frontsurfaces of the members and existing through the outside surface of themembers.

The present invention provides in yet another aspect, an interbodymotion device with a locking device which includes a plate and at leastone leg extending perpendicular from the plate. The locking devicecouples the top body member, bearing member, and bottom body membertogether and inhibit motion therebetween. The interbody motion devicemay also include a relief edge on the front surfaces of the top bodymember, bearing member, and bottom body member and a relief edge on therear surfaces of the top and bottom body members.

The present invention provides in yet another aspect, a fusion implantthat has a first body member having a domed articulation surface and asecond body member having a dished articulation surface. The fusionimplant also has a means to restrict motion when the means is operablypositioned intermediate adjacent to the domed articulation surface ofthe first body member and the dished articulation surface of the secondbody member. The means to restrict motion in the fusion implant includesa plate member for insertion into a front end of the implant and atleast one fastening mechanism for securing the plate member to the firstand second body members.

In yet another aspect, the present invention provides a disc replacementdevice including a first body member, a second body member, a front endand back end, wherein a longitudinal axis extends from the front end tothe back end. The first body member including a flat interior surface,an arcuate exterior surface adjoining the lateral sides of the flatinterior surface, and a concave portion extending into the first bodymember form the flat interior surface. The second body member includinga flat interior surface, an arcuate exterior surface adjoining thelateral sides of the flat interior surface, and a convex portionextending away from the flat interior surface of the second body member.The concave and convex portions are positioned generally centrally alongthe longitudinal axis. When operably positioned, the convex portion ofthe second body member engages the concave portion of the first bodymember to provide for movement therebetween.

The present invention provides in another aspect, a surgical method formaintaining a space between two vertebral bodies in a spine of a patientthat includes the steps of obtaining a medical device that has a firstbody member with a convex articulation surface and a second body memberhaving a concave articulation surface. When the first body member andthe second body member are operably positioned, the convex articulationsurface of the first body member engages the concave articulationsurface of the second body. The method may also include the step ofinserting and coupling a holding tool into an opening within the medicaldevice. The method may further include the step of rotatably insertingthe medical device into a space between two vertebral bodies. The methodmay further include the step of disengaging the holding tool to removethe tool from an opening in the patient.

The surgical method may further include drilling holes through the firstand second openings in the first and second body members into a firstand second vertebra and inserting first and second bone fixation devicesthrough the first and second openings.

Further, additional features and advantages are realized through thetechniques of the present invention. Other embodiments and aspects ofthe invention are described in detail herein and are considered a partof the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of one embodiment of a disc replacementdevice, in accordance with an aspect of the present invention;

FIG. 2 is a perspective view of the disc replacement device of FIG. 1with two inserted bone fixation devices, in accordance with an aspect ofthe present invention;

FIG. 3 is an exploded view of the disc replacement device of FIG. 1, inaccordance with an aspect of the present invention;

FIG. 4 is a perspective view of the disc replacement device of FIG. 1prior to the insertion of two bone fixation devices, in accordance withan aspect of the present invention;

FIG. 5 is a side view of the disc replacement device of FIG. 1 prior tothe insertion of two bone fixation devices, in accordance with an aspectof the present invention;

FIG. 6 is a superior, perspective view of a bottom member of the discreplacement device of FIG. 1, in accordance with an aspect of thepresent invention;

FIG. 7 is a superior, side view of the bottom member of the discreplacement device of FIG. 1, in accordance with an aspect of thepresent invention;

FIG. 8 is a superior, posterior view of the bottom member of the discreplacement device of FIG. 1, implanted within a vertebral body, inaccordance with an aspect of the present invention;

FIG. 9 is an inferior, perspective view of a top member of the discreplacement device of FIG. 1, in accordance with an aspect of thepresent invention;

FIG. 10 is an inferior, side view of the top member of the discreplacement device of FIG. 1, in accordance with an aspect of thepresent invention;

FIG. 11 is an inferior view of the top member of the disc replacementdevice of FIG. 1, in accordance with an aspect of the present invention;

FIG. 12 is an superior view of the superior threaded surface of the topmember of the disc replacement device of FIG. 1, in accordance with anaspect of the present invention;

FIG. 13 is a perspective view of a second embodiment of a discreplacement device, in accordance with an aspect of the presentinvention;

FIG. 14 is an enlarged perspective view of the front aspect of the discreplacement device of FIG. 13, in accordance with an aspect of thepresent invention;

FIG. 15 is an enlarged view of the front aspect of the disc replacementdevice of FIG. 13, in accordance with an aspect of the presentinvention;

FIG. 16 is an exploded perspective view of the disc replacement deviceof FIG. 13, showing a top member, a bottom member and a bearing insert,in accordance with an aspect of the present invention;

FIG. 17 is an exploded front view of the disc replacement device of FIG.13, showing the top member, the bottom member and the bearing insert, inaccordance with an aspect of the present invention;

FIG. 18 is a side perspective view of the bearing insert of the discreplacement device of FIG. 13, in accordance with an aspect of thepresent invention;

FIG. 19 is an inferior view of the bearing insert of the discreplacement device of FIG. 13, in accordance with an aspect of thepresent invention;

FIG. 20 is as side perspective, inferior view of an alternativeembodiment of a bearing insert used in the disc replacement device ofFIG. 13, in accordance with an aspect of the present invention;

FIG. 21 is an inferior view of the alternative embodiment of the bearinginsert of FIG. 20 used in the disc replacement device of FIG. 13, inaccordance with an aspect of the present invention;

FIG. 22 is front elevational view of the disc replacement device of FIG.13, implanted between two vertebral bodies, in accordance with an aspectof the present invention;

FIG. 23 is side elevational view of the disc replacement device of FIG.13, implanted between two vertebral bodies, in accordance with an aspectof the present invention;

FIG. 24 is perspective elevational view of the disc replacement deviceof FIG. 13, implanted between two vertebral bodies, in accordance withan aspect of the present invention;

FIG. 25 is sectional view of the side elevational view of FIG. 23showing the disc replacement device of FIG. 13, implanted between twovertebral bodies, in accordance with an aspect of the present invention;

FIG. 26 is perspective elevational view of an insertion tool for a discreplacement device, in accordance with an aspect of the presentinvention;

FIG. 27 is perspective elevational view of the insertion tool of FIG. 26prior to insertion in the disc replacement device of FIG. 1, inaccordance with an aspect of the present invention;

FIG. 28 is an enlarged perspective elevational view of the insertiontool of FIG. 26 inserted into the disc replacement device of FIG. 1, inaccordance with an aspect of the present invention;

FIG. 29 is a perspective elevational view of the insertion tool of FIG.26 inserted into the disc replacement device of FIG. 1 followingimplantation of the disc replacement device between two vertebralbodies, in accordance with an aspect of the present invention;

FIG. 30 is a partially exploded perspective view of an alternativeembodiment of a disc replacement device, showing a top member, a bottommember and a means to restrict motion, in accordance with an aspect ofthe present invention;

FIG. 31 is a perspective view of the assembled alternative embodiment ofa disc replacement device seen in FIG. 30 with the fixation screws inposition, in accordance with an aspect of the present invention;

FIG. 32 is a partially exploded perspective view of an alternativeembodiment of a disc replacement device, showing a top member, a bottommember and an alternative embodiment for a means to restrict motion, inaccordance with an aspect of the present invention;

FIG. 33 is a perspective view of the assembled alternative embodiment ofa disc replacement device seen in FIG. 32 with the fixation screws inposition, in accordance with an aspect of the present invention;

FIG. 34 is a partially exploded perspective view of an alternativeembodiment of a disc replacement device, showing a top member, a bottommember and an alternative embodiment for a means to restrict motion, inaccordance with an aspect of the present invention;

FIG. 35 is a perspective view of the assembled alternative embodiment ofa disc replacement device seen in FIG. 34 with the fixation screws inposition, in accordance with an aspect of the present invention; and

FIG. 36 is an elevational view of an alternative embodiment of a discreplacement device, showing a top member, a bottom member and analternative embodiment for a means to restrict motion that includes aplurality of superior to inferior extending screws, in accordance withan aspect of the present invention.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

Generally stated, disclosed herein is a disc replacement device orinterbody dynamic disc implant that typically includes a top member, abottom member and a removable bearing insert. An alternative embodimentof the disc replacement device may include a top member with an integralbearing component and a bottom member with an integral articulatingcomponent. As used herein, the terms “disc replacement device”,“device”, “interbody disc implant,” “interbody motion device,” and“implant” may be used interchangeable as they essentially describe thesame type of device. Further, a corresponding insertion tool used forthe implantation of the disc replacement device is discussed. Finally,described herein is a surgical method (both open and minimally invasive)for using the disc replacement device to maintain a space between twovertebral bodies within a patient suffering from a diseased or damageddisc within the spinal column.

In this detailed description and the following claims, the wordsproximal, distal, anterior, posterior, medial, lateral, superior andinferior are defined by their standard usage for indicating a particularpart of a bone or implant according to the relative disposition of thenatural bone or directional terms of reference. For example, “proximal”means the portion of an implant nearest the torso, while “distal”indicates the portion of the implant farthest from the torso. As fordirectional terms, “anterior” is a direction towards the front side ofthe body, “posterior” means a direction towards the back side of thebody, “medial” means towards the midline of the body, “lateral” is adirection towards the sides or away from the midline of the body,“superior” means a direction above and “inferior” means a directionbelow another object or structure.

It is shown in FIG. 1, the example of the disc replacement device 100.The device 100 as seen in FIGS. 1, 2, 3, 4 and 5 has a generallycylindrical geometry with an either straight or tapered external profileto facilitate insertion between two vertebral bodies. The implant 100may likely include a top member or second body member 110 and a bottommember or a first body member 120. As seen in FIG. 2, for examplepurposes, two bone fixation devices or bone fasteners 130 are insertedthrough the front aspect of the top member 110 and bottom member 120 toenhance stability of the device following insertion between thevertebral bodies. The top and bottom members 110, 120 may also includerear aspects parallel to the front aspects. The bone fixation devices130 as seen in FIGS. 2 and 3 are cancellous bone screws although otherfixation devices may be employed, including but not limited to posts,deployable fins, alternative threaded screws, nails, pegs and pins.Various surface coatings may be applied to these fixation devices toenhance securement to the bone.

As depicted in FIGS. 2 and 3, the bone fixation devices are insertedthrough two respective holes 140 that extend at an angle from the frontface of the top member 110 and the bottom member 120 through theexternal superior surface 150 and the external inferior surface 150 ofthe respective top member 110 and bottom member 120, respectively. Theexternal superior surface 150 and external inferior surface 150 may havea generally arcuate shape. For example purposes, the trajectory of theholes may be within a range of between 10 and 45 degrees with apreferred angulation of 30 degrees. It is contemplated that the holesmay be configured to allow for variable angulation of the screws tofacilitate bone purchase when insertion occurs. The diameter of theholes may be between 2.5 and 5.5 mm with a preferred diameter of 3.5 mm.The entry port 141 for the hole may allow for rotation or pivoting ofthe corresponding bone fixation device head or alternatively, the holeopening may provide for a mechanism to lock the bone fixation devicehead in a set position.

FIGS. 4 and 5 show the top member 110 and the bottom member 120operatively positioned relative to each other. The resultinglongitudinal profile of the device cylindrical structure may be straightor incorporate a slight taper. The overall length of the cylinder mayrange from 35 to 55 mm with a preferred length of approximately 44 mm.As seen in FIG. 5, a chamfer, relief, relief edge, radius, or other likematerial break 111 is present to facilitate movement between the top andbottom members.

The device 100 as shown has a diameter of approximately 17 mm, althoughit is understood that the device may be offered with a wide range ofdiameters to accommodate the various clinical situations that arepresented. The range of diameters may be between 12 and 25 mm with apreference cross-section of approximately 17 mm.

FIGS. 4, 5, and 12 show the external surfaces 150 for both the topmember 110 and the bottom member 120 to be threaded. The threads 151 runcontinuously for the entire circumference and length of the device. Forexample purposes, as shown in these figures, the thread configuration isa buttress thread with a thread depth of 1 mm, the thread type and depthmay be altered depending upon the quality of bone into which the device100 is being threaded. As seen in FIG. 8, the thread configuration willallow for variable depth of penetration into the vertebral endplate. Forexample purposes, as shown in FIG. 8, the depth of penetration into thebone is approximately 3 mm. It is also contemplated that the externalsurface 150 and corresponding threads 151 may be coated in some mannerwith a bone growth substance, including but not limited to TCP, HA, MPor other similar material. It is further contemplated that the externalsurfaces 150 may be non-threaded and that such surfaces may beconfigured with alternative surface engaging structures, including butnot limited to, ribs, spikes, scallops, and porous coating.

FIG. 5 exhibits the continuity of the threads 151 between the top andbottom members when the two members are operatively positioned. Havingthe threads 151 run in a continuous circumferential manner allows theoperating surgeon to screw the device 100 into two adjacent vertebralendplates while maintaining the alignment and orientation of the topmember 110 and bottom member 120 relative to each.

Looking at the bottom member 120 alone, FIGS. 6 and 7 show generally theconfiguration of this aspect of the device. The member 120 as shown is asolid body, although it may be a hollow construct. As described above,the external surface 150 is threaded. The superior aspect of the bottommember 120 is comprised of a flat surface or portion 122 that runs theentire length of the bottom member 120. Positioned in the central regionof the flat surface 122 is an arcuate or ball-shaped element 123 thatextends from the flat surface 122. (Other spherical shapes may also beused for the arcuate element or convex portion 123). The arcuate element123 creates a convex articulation surface. The “ball” is typically 14 mmin diameter although the device 100 may be available with various sizedballs ranging between 10 and 20 mm. As seen in FIG. 7, the arc of theball (as measured from one side of the flat surface to the opposite sideof the flat surface) as shown is slightly less than 180 degrees,although it is contemplated that device 100 be made with a varying arcof between 140 and 180 degrees with a preferred included angle of 150degrees. The surface 124 of the ball is smooth to allow for low frictionarticulation with the top member 110.

The top member 110 is shown alone in FIGS. 9, 10 and 11. Like the bottommember 120, the top member 110 may be a generally solid construct. Asshown in these figures, the inferior aspect of the top member 110 iscomprised of a flat surface or portion 112 with a concavity or arcuatedepression 113 located along the device midline and is centralizedrelative to the outer perimeter of the top member 110. The arcuatedepression or concave portion 113 creates a concave articulationsurface. The diameter of the depression or “socket” 113 is sized toreceive the ball 123 and provide for low friction movement between thetop member 110 and the bottom member 120. The socket 113 surface isprepared in a manner to ensure the socket 113 functions as a bearingsurface to facilitate smooth articulation between the top member 110 andthe bottom member 120.

Although not shown with the embodiment of the device 100 it iscontemplated that the socket 113 may not be comprised of a constantradius but include a relatively flat portion at the apex resulting in atrough like depression (See FIG. 20). For example purposes, the lengthof the flat portion may allow the ball 123 to translate over a certaindistance either in the anterior to posterior direction or alternatively,in the medial to lateral direction when the top member 110 isarticulated through a full range of motion relative to the bottom member120. The length of the flat portion in the trough depression may bevaried depending upon a given clinical situation to provide theoperating surgeon with the flexibility to adjust the resultant amount oftranslation required for a particular patient.

As seen in FIGS. 1, 2 and 3, ball 123 of bottom member 120 articulateswithin the socket 113 of top member 110. When operatively positioned,the device 100 will allow for a full range of between 10 and 20 degreesof anterior/posterior or flexion/extension motion. Preferably, the fullrange of motion will be between 13 and 15 degrees of flexion/extension.This equates to approximately 6½ to 7½ degrees of flexion and an equalamount of extension as measured from a neutral position. It should benoted that the device final range of motion may be impacted by theamount of thread contact that occurs with the bone following theinsertion of the device 100 into the adjacent vertebral bodies, such asa first vertebra and a second vertebra. Additionally, the device 100 isconfigured to allow for a range of lateral bending of between 4 and 12degrees, with the preferred range being between 6 and 10 degrees. Thisequates too approximately between 3 and 5 degrees for each side oflateral bending. The device 100 in operation may flex and extend at thesame time that lateral bending motion is occurring. Finally as notedabove, in the event that a trough depression is used within the topmember, along with the flexion/extension and lateral bending motion,anterior to posterior translation may also be occurring. The distance ofsuch translation will depend upon the length of the flat portion withinthe trough depression. It should be understood that the ranges of motionprovided above are for examples purposes only and may increase ordecrease depending upon several structural elements of the device 100 aswell as anatomic features of the patient.

A second embodiment of disc replacement device 200 is shown in FIGS.13-17. The device 200 as seen in the exploded views of FIGS. 16 and 17has a generally cylindrical or arcuate geometry similar to device 100with an either straight or tapered external profile to facilitateinsertion between two vertebral bodies. The implant 200 may likelyinclude a top body member 210, a bottom body member 220, two bonefixation devices 230 (see FIGS. 13 and 14) which are inserted throughthe front aspect of the top and bottom members 210, 220 to enhancestability of the device following insertion between the vertebralbodies. The top and bottom members 210, 220 may also include rearaspects parallel to the front aspects. Also seen is a third element, amodular bearing insert 270 that couples with the top member 210. As usedherein, the terms “modular bearing insert,” “bearing member,” “bearinginsert” and “replaceable bearing insert” may be used interchangeable asthey each refer to the same component. Both of the devices 100, 200 havesimilar structural members, so for brevity sake, these same elementswill not be discussed again and it should be understood that thelimitations disclosed above for device 100 are the same as for device200. These same elements include the bottom member 220 including ball223, the bone fixation devices 230, the holes 240 and the externalsurface 250.

Top member 210 is modular in design in that it includes a replaceablebearing insert 270. The bearing insert 270 is slid into a channel 212that is positioned between two retaining mechanisms, which for exampleis shown in FIG. 15 as a lip or dovetail arrangement 211. The bearinginsert 270 as seen in FIG. 18 is generally rectangular in shape to fitwithin the corresponding channel 212 in the top member 210. The bearinginsert 270 includes a flat top surface 213, a flat bottom surface 214with a depression or “socket” 215. As shown in FIG. 19, the diameter ofthe socket 215 is sized to receive the ball 223 of the bottom member 220and provide for low friction movement between the top member 210 and thebottom member 220. The socket 215 surface is prepared in a manner toensure the socket 215 functions as a bearing surface to facilitatesmooth articulation between the top member 210 and the bottom member220. The modular bearing insert 270 provides the operating surgeon withflexibility to adjust the overall device thickness and ensure properspacing between the two vertebral bodies has been achieved.

As seen in FIGS. 20 and 21, socket 215 may also be elongated orconfigured more like a trough to allow for translational movementbetween the bearing insert 270 and the ball 223. As described above, atthe apex of the socket 215 a flat portion 216 exists that allows theball 223 to slide rather than roll along the surface of the socket 215.From a functional perspective, this means that when assembled, topmember 210 would allow bottom member 220 to translate a finite distancebefore rolling or pitching motion occurs following the implantation ofthe device between two adjacent vertebral bodies.

The method of assembling the top member 210 may include the steps ofchoosing which configuration of the socket 215 the operating surgeonwould like to utilize. Following the selection, the surgeon would slidethe bearing insert 270 into the retention mechanisms, which as shown inFIGS. 14 and 15 are dovetails 211. The device 200 is then assembled withthe top member 210 and bottom member 220 being screwed together into theadjacent vertebral bodies. Following insertion into the bones, the bonefixation devices 230 are inserted through holes 240. As seen in FIG. 13,the heads of the bone fixation devices 230 will lock the bearing insert270 into the channel 212 of the top member 210. It is understood thatother locking mechanisms or anti-kickout devices may be used, includingswags, spring locks, pins, press-fit locks, etc. Please note that theholes 240 and entry ports 217 and the resultant angulation of the bonefixation devices 230 are similar to those described above for device100.

Several biocompatible materials may be used to fabricate the elements,including the insert, of both embodiments of the disc replacement device100, 200. These may include a myriad of metals, polymers, ceramics andcomposites. Examples of these include PEEK, titanium and stainlesssteel.

FIGS. 26-29 show an insertion instrument 500 that may be used withdevices 100, 200. The instrument 500 includes a handle 501 and analignment head 502. The head 502 may include a spacer 503 and at leastone prong 504. The example instrument 500 is shown with a superior andinferior prong 504.

FIG. 27 shows the instrument 500 in position prior to insertion into thedevice 100, 200. The prongs 504 are seen to be aligned with the holes140, 240 of the devices and the spacer 503 positioned to slide in thegap that exists between the top member 110, 210 and bottom member 120,220 when these two elements are operatively positioned.

FIG. 28 further shows the instrument 500 following engagement with thedevice 100, 200. The prongs 504 extend into the holes 140, 240 while thespacer 503 slides into the slot that exists between the two assembledmembers. The head 502 is juxtaposed to the front portions to the top andbottom members, 110, 210 and 120, 220 respectively. As seen in FIG. 29,the instrument is used to insert the device 100, 200 into the space thatexists between two adjacent vertebral bodies. The instrument 500 ismulti-functional in that it holds the assembled device 100, 200 togetherfor threading the device into the bone. The instrument 500 may also beused to actually thread the device 100, 200 into the bone. Further,although not shown, the instrument 500 may function as a drill guide fordrilling the pilot holes into which the bone fixation devices 130, 230are inserted.

The example surgical method for using either of the embodiments of thedisc replacement devices 100, 200 is well known in the art, includingthe appropriate lateral surgical exposure and dissection techniques.However, the devices 100, 200 may be inserted using two distinctlydifferent surgical procedures, one using an open exposure, oralternatively, using minimally invasive techniques. In the opentechnique, a long oblique incision is made on the patients flank andgeneral abdominal retractors are used to expose the abdominalmusculature. The muscles are opened and similarly retracted. Afterdissecting the retroperitoneal space the iliopsoas muscle is retractedand the disc space is exposed. The disc space is then drilled, tappedand the device 100, 200 is inserted and held in place with the lockingscrews 230 through the insertion holes 240. In the minimally invasivetechnique the procedure is modified to be performed through a 3 cmincision. All muscle and soft tissue is retracted via tubular retractorsinserted over a series of dilators based a guide wire inserted into thedisc space. Thereafter, the same procedure is performed, but through theminimal access tubular retractor.

The method includes, obtaining the properly sized and configured device100, 200 relative to the target vertebral end plates that will beopposing the external surfaces of the top member and the bottom member.A pilot hole is drilled that transects the interbody space following theresection of the diseased/damaged disc. An insertion tool 500 is used toengage and secure the assembled device 100, 200. The insertion tool 500is positioned adjacent the pilot hole with the assembled device 100, 200locked to the proximal end. The insertion instrument 500 with theassembled device 100, 200 is rotated, screwing the device 100, 200 intothe pilot hole until the device 100, 200 is appropriately positionedwithin the vertebral end plates of the adjacent vertebral bodies.Imagining technology is used to confirm proper spacing and positioninghas been achieved. Once this is confirmed, the insertion tool isdisengaged and removed from the body.

The additional steps of drilling the holes and inserting the bonefixation devices 130, 230 may also be completed once the device 100, 200is in its final position.

FIGS. 22-24 show various views of the device 100, 200 in between twovertebral bodies with the bone fixation devices 130, 230 secured throughthe device and into the adjacent bone. A side sectional view of theimplanted device 100, 200, including the bone fixation devices 230 isseen in FIG. 25. The sectional view shows how the ball 223 and thebearing insert 270, specifically the socket 215 are aligned. The bonefixation devices 230 are also shown as locking the bearing insert 270 inposition so as to ensure no movement of the bearing insert 270 whenarticulation occurs between the top and bottom members 210, 220.

Further embodiments of a disc replacement device are seen in FIGS.30-36. Specifically, as seen in the exploded views shown in FIGS. 31, 33and 35 and also an elevated view as shown in FIG. 36, a means torestrict motion 650 between the top and bottom members 610, 620 isincluded to convert the disc replacement device from a motion device100, 200 to a fusion device 600. The same structural elements asdescribed above for device 100 are seen in device 600, but for brevitysake, these will not be described again in detail here as such elementswill include the same characteristics and functionality as disclosedabove.

FIG. 36 shows for example, the means to restrict motion as a pluralityof screws 651 that are inserted through the top member 610 into thebottom member 620 on each side of the articulating surfaces 612, 622,thereby fixating the two members together and inhibiting motiontherebetween. After the device 600 has been fixed, it can be threadedinto the upper and lower vertebral bodies creating a space into whichfusion material can be packed to facilitate stabilization and fusionbetween the vertebral bodies.

Alternatively, as seen in FIGS. 30-35, the means to restrict motion mayalso include a locking device, such as a “T-pin” or T-shaped member 652(with screws) (see FIGS. 30 and 31), a “U-pin” or U-shaped member 653(see FIGS. 32 and 33) or a “U-pin” or U-shaped member with middle spacer654 (see FIGS. 34 and 35). The means to restrict motion 650 for theembodiments seen in FIGS. 30-35 may be inserted into the ends of the topmember 610 and bottom member 620 on both sides and lateral to thearticulating surfaces 612, 622. These three examples of types of meansto restrict motion provides the surgeon with the option to change thedevice 600 from a dynamic device into a static or fusion devicepost-insertion between the vertebral bodies. For these embodiments themeans to restrict motion is inserted into the ends of the top member 610and bottom member 620 on both sides and lateral to the articulatingsurfaces 612, 622. A portion (pins, posts, screws, deployable fins,ribbed cylinders, tapered posts, etc.) of the means to restrict motionor at least one protrusion is (are) inserted to a depth into the top andbottom members 610, 620 to immobilize the two members relative to eachother. The at least one protrusion 654, 656 extends perpendicular from aplate 658 which mates with the front aspects of the top member 610 andbottom member 620. The at least one protrusion 654 may be a centerprotrusion of insertion into the opening between the top and bottommembers 610, 620. Alternatively, the at least one protrusion 656 may belegs around the perimeter of the plate 658, in the depicted embodimentthere are four protrusions 656 at the corners of the plate 658. In yetanother embodiment, the at least one protrusion 656 may include both acenter protrusion and at least one leg positioned on the perimeter ofthe plate 658. The plate 658 may include openings 660 for inserting atleast one fastener 662 into the top member 610 and bottom member 620 tofix the members 610, 620 together. In the depicted embodiment of FIGS.30 and 31, there are four openings 660 and four fasteners 662. Oncefixed, the implanted device 600 may, optionally, be rotated 90 degreesfrom its original insertion position. The space between the top member610 and bottom member 620 is positioned to create a channel or spanbetween the upper and lower vertebral bodies that will accommodatefusion material and enable bone fusion to occur across the distancebetween the two vertebral bodies.

Although the example embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions and substitutions can be madewithout departing from its essence and therefore these are to beconsidered to be within the scope of the following claims.

What is claimed is:
 1. A surgical method for maintaining a space betweentwo vertebral bodies in a spine of a patient, comprising: obtaining amedical device comprising: a bottom body member having an outer surface,an inner surface, and a first opening extending through the bottom bodymember to the outer surface, wherein a portion of the inner surface isconvex; a top body member having an outer surface, an inner surface, anda second opening extending through the top body member to the outersurface, wherein the inner surface defines a channel; and a bearinginsert member having a flat top surface and a bottom surface comprisinga concave portion; assembling the medical device by sliding the bearinginsert member within the channel to operatively connect the bearinginsert member to the channel of the top body member, and positioning thebearing insert member relative to the bottom body member such that theconcave portion of the bearing insert member articulates with the convexportion of the bottom body member; obtaining a holding tool having ahandle and a head extending away from a first end of the handle, whereinthe head includes a spacer and at least one prong; inserting the spacerinto a gap within the medical device and the at least one prong into atleast one of the first opening and the second opening to couple theholding tool within the medical device; inserting the medical deviceinto the space between the two vertebral bodies; and disengaging theholding tool to remove the holding tool from an opening in the patient.2. The surgical method of claim 1, further comprising: drilling a firsthole through the first opening in the bottom body member into a firstvertebra and drilling a second hole through the second opening in thebearing insert member and the top body member into a second vertebra;and inserting a first bone fixation device through the first opening anda second bone fixation device through the second opening.
 3. Thesurgical method of claim 2, wherein inserting further comprisesrotatably implanting the medical device into the space between the twovertebral bodies using a surgical procedure selected from an openexposure procedure and a minimally invasive technique.
 4. The surgicalmethod of claim 3, further comprising: inserting the first bone fixationdevice into the first opening and the second bone fixation device intothe second opening; and securing the medical device to the two vertebralbodies.
 5. The surgical method of claim 2, wherein the top body memberincludes a front surface and a rear surface, the bearing insert memberincludes a front surface, and the bottom body member includes a frontsurface and a rear surface.
 6. The surgical method of claim 5, whereinthe first opening in the bottom body member extends from the frontsurface of the bottom body member to the outer surface of the bottombody member; and the second opening in the top body member extends fromthe front surface of the top body member to the outer surface of the topbody member.
 7. The surgical method of claim 6, wherein the firstopening and the second opening are each angled, wherein the angles rangefrom about 10 degrees to about 45 degrees.
 8. The surgical method ofclaim 5, wherein the front surfaces of the top body member, the bearinginsert member, and the bottom body member include a front relief edgeand the rear surfaces of the top body member and the bottom body memberinclude a rear relief edge.
 9. The surgical method of claim 2, whereinthe two bone fixation devices are selected from bone screws, posts,deployable fins, nails, pegs, and pins.
 10. The surgical method of claim1, wherein the concave portion of the bearing insert member isconfigured as at least one of a sphere and a ball to permit at least oneof translation and rotation of the convex portion of the bottom bodymember.
 11. The surgical method of claim 1, wherein the outer surfacesof the top body member and the bottom body member are generally arcuate.12. The surgical method of claim 11, wherein disposed on the outersurfaces of the top body member and bottom body member are at least oneof threads, ribs, spikes, scallops, and porous coating.
 13. The surgicalmethod of claim 11, wherein the outer surface of the top body member andthe bottom body member are coated with a bone growth sub stance.
 14. Thesurgical method of claim 1, further comprising: a locking deviceincluding a plate and at least one leg extending perpendicular from theplate.
 15. The surgical method of claim 14, wherein the at least one legis disposed between the top body member and the bottom body member andthe plate of the locking device pressingly contacts the front surfacesof the top body member, the bearing insert member and the bottom bodymember.
 16. The surgical method of claim 14, wherein the locking platefurther comprises at least two openings.
 17. The surgical method ofclaim 16, wherein the locking device further includes at least twofastening mechanisms for insertion through the at least two openings andextending through the plate and into at least two of the top bodymember, the bearing insert member, and the bottom body member to couplethe top body member, the bearing insert member, and the bottom bodymember together.
 18. The surgical method of claim 1, wherein the topbody member and the bottom body member are comprised of a biocompatiblematerial, selected from the group comprising: PEEK, titanium, cobaltchromium and stainless steel.
 19. The surgical method of claim 1,wherein the bearing insert member is modular.